em i think the girl and his dad were doing naughty things and he saw and he masturbated and was scared and crying, the girl called him disgusting so maybe his trauma is from this. But still not sure what happened for him to masturbate, it is a possibility.
but wasn't he too young to masturbate...???
Maybe he just tried to imitate the two of them doing naughty things, like putting fingers in his ass... and discovered masturbation
I think he´s just sitting in his own pee. Frightend children often pee themselves.
after rereading the most recent chapter, i just realized that shirotani's pants were around his knees, i still don't understand the flashback just yet. initially, i thought the panting was coming from the girl and shirotani's dad, but it appears it was coming from shirotani himself.